The present invention relates to an air bag device, more particularly, to an air bag device which can securely restrain the knees of an occupant and reliably receive the upper body of the occupant.
The air bag device is a passive restraint system for efficiently protecting an occupant from impact generated at a collision.
When a vehicle comes into collision, the occupant is forced to move forward because of inertial force. As for the air bag device, an air bag filled with gases receives the moving occupant particularly at his/her chest and head. Therefore, the occupant is protected from a secondary collision inside the vehicle.
In case of an air bag device for a driver (hereinafter, referred to as a driver air bag device), an air bag thereof is usually folded and accommodated in a center pad of a steering wheel. In a collision, the air bag is inflated between the steering wheel and the driver, thereby preventing the driver from bumping against the steering wheel.
Recently, an air bag device for protecting an occupant in a passenger seat or a rear seat (hereinafter, referred to as a passenger air bag device) has been also developed for practical use. There is no steering wheel in front of the passenger seat differently from the driver's seat. There is therefore a wide space between the occupant in the passenger seat and an instrument panel. Accordingly, an air bag of the passenger air bag device has a large volume. Conventionally, the volume of the air bag of the passenger air bag device is nearly 2.5 times as much as that of the air bag for the driver air bag device and the passenger air bag device then requires an inflator having a large capacity. FIG. 1 is an explanatory view of a conventional passenger air bag device 50. As shown in FIG. 1, a container 52 in which an air bag is accommodated is installed in the upper portion of an instrument panel 51. The air bag is folded and then accommodated inside the container 52. Reference numeral 50A designates the folded air bag in the accommodated state. The air bag is inflated just in front of an occupant 53 and then occupies a space in front of the upper body of the occupant 53 when the air bag is fully inflated. Reference numeral 50B designate the air bag fully inflated.
However, the air bag 50B cannot restrain the lower body of the occupant as shown in FIG. 1.
Techniques for solving such a problem are disclosed in Japanese Patent Publication No. S57-54337, U.S. Pat. No. 4,265,468 and so on.
An air bag device 60 disclosed in Japanese Patent Publication No. S57-54337 is provided with two air bags, one of which is a torso bag 61 and the other one of which is a knee bag 62, as shown in FIG. 2. When the vehicle comes into collision, the torso bag 61 and the knee bag 62 are simultaneously inflated, with the result that the knee bag 62 restrains the knees of the occupant 53. Therefore, the knee bag 62 prevents the lower body of the occupant 53 from moving forward and the torso bag 61 receives the upper body of the occupant 53.
In the air bag device 60, the two air bags 61 and 62 which have different volumes from each other are simultaneously inflated by only one inflator 64. The knee bag 62 requires an internal pressure higher than that of the torso bag 61. The air bag device 60 has a container which accommodates not only the air bags 61, 62 and the inflator 64 but also an air path supporting plate 65 and a one way valve 66. According to the aforementioned structure, the air bag device 60 provides high pressure gases into the knee bag 62 and provides gases, the pressure of which is suitable for inflating the torso bag 61, into the torso bag 61. Accordingly, the air bag device 60 has a complex structure and the size of the air bag device 60 is increased.
As for an air bag device disclosed in U.S. Pat. No. 4,265,468, a lower cover 55 is mounted on the instrument panel 51 positioned in front of the passenger seat as shown in FIG. 3. An air bag 70 (not shown in the folded state) and an inflator 71 are accommodated inside the lower cover 55. In a collision, the air bag 70 is inflated inside a cabin of the vehicle by opening a lid 75 of the lower cover 55. As mentioned above, the air bag 70 is inflated from a lower position near the knees of the occupant 53, thereby restraining the knees and the upper body of the occupant 53. In addition, the air bag 70 has a knee cushion 73 inside thereof, which securely prevents the lower body of the occupant 53 from moving forward.
In the air bag device disclosed in U.S. Pat. No. 4,265,468, the air bag 70 is inflated inside a cabin of the vehicle by opening a lid 75 of the lower cover 55 positioned in front of the knees of the occupant 53. Accordingly, the air bag 70 requires a large volume to occupy a space between the lower position and the upper position in front of the occupant 53. In addition, to inflate the air bag 70 having such a large volume, the inflator requires a large capacity, thereby making the air bag device expensive.